The longterm aims of the project are threefold: 1) To study normal interlimb coordination in the cat as an entry to understanding the neural control program for locomotion, 2) To relate peripheral afferent input to the functions of the central program, and 3) To determine the role of the cerebellum in promoting normal stepping. Information as to normal and perturbed locomotion in the cat is counterpart to information on human gait, and a particular emphasis of the proposed work is to develop methods of data collection, data analysis, and perhaps even training or re-training procedures that will be compatible with the study of human motor pathologies. The short-term goals will continue, for aim 1, to quantify normal locomotion in terms of footfall patterns, selected joint angle excursions, and electromyographic analysis. Efforts will be continued to optimize performances (by a judicious use of different reinforcement contingencies based on food or the avoidance of, e.g., an air jet) on a motor-driven treadmill. The subsequent assessment will characterize stepping as a function of steady-state and varying velocities, in conjunction with computerized pattern recognition techniques. Aims 2 and 3 will emphasize, at first, effects of subtotal deafferentation of the limbs and lesions of the deep cerebellar nuclei upon stepping.